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In this episode of Longevity by Design, our hosts, Dr. Gil Blander and Ashley Reaver, MS, RD, CSSD, are joined by Dr. Matt Johnson. Dr. Johnson is the Director of Clinical Research at Dexcom—a leading company in diabetes care through the use of continuous glucose monitoring. With extensive knowledge in diabetes, metabolic health, and exercise physiology, Dr. Johnson talks through his research and gives insight into the latest science in the field of longevity.
Dr. Matthew Johnson is the Director of Clinical Research at Dexcom. Dexcom is transforming diabetes care by developing continuous glucose monitoring systems for ambulatory use by people with diabetes and healthcare providers. Dr. Johnson performs clinical research for existing and new product development, including building capabilities for analytes beyond glucose. Dr. Johnson received his PhD in Integrative Biology from the University of California Berkeley.
Continuous glucose monitoring (CGM) systems sense glucose in the subcutaneous fluid to approximate blood glucose concentration in an individual. CGM monitors are small wearables with a sensor just under the skin, measuring glucose concentration in the interstitial space. This wearable then sends a glucose reading to a handheld device every 5-10 minutes and will alert the individual if their glucose level is too high or too low.
CGM differs from finger prick glucose monitors, as the finger prick method directly measures capillary (blood) glucose. Due to the slight lag between the interstitial fluid and blood, CGM companies use an algorithm to estimate blood glucose concentration at a given time based on the value measured in the interstitial space.
Continuous glucose monitors are most commonly used by those with diabetes. Dr. Johnson notes that more than five million patients globally currently use this technology; however, the industry aims to make CGM more accessible. “Within the global diabetes population, the percentage of people with access to CGM is still in the single digits. The global scale of manufacturing and improving access through demonstrating clinical evidence, market access, and getting costs down are initiatives that the industry is working on,” Dr. Johnson explains.
As CGM grows and develops, people can leverage this technology outside of diabetes care. For example, Dr. Johnson states that CGM use has become increasingly popular among European athletes. Athletes use this technology to measure metabolic health and fine-tune their diets based on their body's reactivity to specific foods.
Beyond diabetes patients and athletes, continuous glucose monitoring can also be used to understand how different lifestyle factors impact blood glucose levels. "When you start seeing five-minute data collected over multiple days, it's surprising what foods impact your glucose. From a health and wellness perspective, it can be very insightful for people to understand how stress, sleep, different forms of exercise, and specific foods impact their glucose—and then, of course, what this means clinically," explains Dr. Johnson.
Measuring subcutaneous fluid has opened a new door to personalized nutrition. Using this technology, we'll soon be able to measure other analytes, such as ketones, alcohol, and lactate. "It's exciting because as we start measuring those analytes individually and eventually in conjunction, people can learn about their bodies and understand their metabolism like never before. You're no longer seeing just a point in time reading, but you're starting to see how your daily activities, habits, and behaviors impact your metabolism," says Dr. Johnson.
Now you may be wondering, why is glucose so important to measure? In the short term, consistently high blood glucose levels can lead to dehydration, lack of energy, fatigue, brain fog, and shakiness. If left unchecked, high blood glucose and HbA1c levels are associated with an increased risk of age-related diseases like metabolic syndrome and cardiovascular disease. Higher fasting blood glucose levels are also associated with an increased risk of early death from any cause (or what's known as all-cause mortality). As a subject matter expert, Dr. Johnson describes how glucose impacts our metabolic health.
The key regulator of glucose metabolism is insulin—a powerful hormone released in response to rises in blood glucose concentration, typically following a meal. Many tissues in the body are responsive to insulin, including the liver, skeletal muscle, and adipose tissue. Insulin causes these tissues to take up glucose from the blood and store it, or in the case of the liver, to stop releasing more glucose into the bloodstream. Dr. Johnson explains that insulin resistance leads to pre-diabetes, meaning the cells aren't as responsive to insulin. If blood glucose concentrations are uncontrolled, they can lead to type II diabetes.
In addition to his extensive knowledge of diabetes and metabolic health, Dr. Johnson is also knowledgeable in exercise physiology. Dr. Johnson reiterates the importance of exercise and its many benefits on the body.
A key physiological benefit of exercise is its impact on mitochondrial content. Mitochondria is an organelle in our cells that generate energy for the body. High mitochondrial content has been linked to healthy aging and increased athletic performance, making it a marker of interest for longevity.
Dr. Jonson explains how exercise impacts mitochondria, “If you take a muscle biopsy of an elite athlete and isolate the mitochondria, you’ll see they typically have two to three times more content. Also, their ability to consume substrates—for example, fatty acids, glucose, lactate—is extremely high.” Both HIIT workouts and endurance training improve mitochondrial health.
Another marker that improves with exercise is Vo2 max. Vo2 max measures the maximum amount of oxygen your body can utilize during exercise. Vo2 max is also associated with healthy aging—low Vo2 max in older individuals puts them at increased risk for a cardiovascular event. Dr. Johnson says that habitual exercise leads to lower risk for many chronic diseases and improves cardiovascular function—all related to Vo2 max.
Unsurprisingly, mitochondrial content is also correlated with Vo2 max. Dr. Johnson says that individuals with low mitochondrial content typically have a lower Vo2 max and vice versa. What is interesting, however, is that exercising into late adulthood has shown to have lasting effects on both measurements. "We've done studies on individuals into their seventies, and if they're regularly exercising and performing aerobic exercise, they can have mitochondrial content similar to those in their twenties," Dr. Johnson explains. He says that Vo2 max is also higher in older persons who have lived an active life, which sets them up nicely for performing activities of daily living and decreasing their risk for cardiovascular events.
Dr. Johnson’s top tip for improving health is to be physically active. He specifically encourages making exercise a lifelong habit by finding exercise you enjoy. Dr. Johnson closes by saying physical activity improves health and quality of life in countless ways and is the key to healthy aging.